Effects of Eurycoma longifolia supplementation: An evaluation of cell growth, exercise performance and wellbeing in adult males

Eurycoma longifolia is often prescribed in complementary and alternative medicine. The extract has gained a reputation for boosting sexual performance, mood, muscle mass, and strength by increasing testosterone levels in males facing low testosterone levels, stress, and lack of energy due to ageing. E. longifolia has demonstrated the ability to regulate testosterone production by affecting the hypothalamic-pituitary axis in animals, but this phenomenon has not been thoroughly examined in humans. Even though studies are limited, E. longifolia supplementation has shown improvement in exercise performance and wellbeing. This murine and human study has four primary aims: (1) to examine the cytotoxicity of E. longifolia on skeletal muscle cells; (2) to elucidate the effect of E. longifolia supplementation in terms of selected reproductive hormonal changes; (3) to compare the short-term versus long-term effects of E. longifolia supplementation on psychological mood state and sexual function among young participants; (4) to determine the ergogenic properties of E. longifolia with regard to exercise performance following supplementation among young participants. This work’s main findings show higher cytotoxicity levels in the control treatment (CON) treated with a differentiation medium compared to skeletal muscle cells (SMC) treated with E. longifolia. An increase in lactate dehydrogenase activity was observed from 96 to 144 hours with a 4.4, 3.8 and 3.3 (CON > 0.5 mg/ml > 1.0 mg/ml) fold increase and 4.4, 3.3 and 3.9 (CON > 1.0 mg/ml > 0.5 mg/ml) fold increase in passage 13 and 26, respectively. While findings have shown that SMC exposure to E. longifolia treatment did not exhibit any toxicity, there is an increase in cell viability in E. longifolia treated cells. With regard to hormonal changes, short-term supplementation of 600 mg/day showed an increase in testosterone (0.97 ng/ml, 11.1%; p = 0.004), while long-term supplementation showed an increase up to week 4, then a decrease (0.142 ng/ml, 2%; p > 0.05) at week 8. Neither short nor long-term supplementation showed any significant changes in luteinising hormone (LH) and estradiol. Findings also show that the changes in testosterone are not due to the extract influencing the hypothalamic-pituitary gland axis. In addition, the dosage did not exhibit deleterious effects on liver functions, demonstrating that supplementation E. longifolia for 8 weeks is safe for consumption. When investigating duration, short-term supplementation of E. longifolia demonstrated an improvement in mood state domains, such as anger (5.12%) and fatigue (11.09%); long-term supplementation seemed to affect tension (8.19%) and anger (4.14%). These findings indicate that supplementation of E. longifolia improves certain mood state domains, indicating that this extract may be an effective remedy to improve daily mood states affected by daily stress. Meanwhile, the sexual function test was measured through self-reported data. Short-term supplementation showed improvement in the ejaculation domain (6.13%), and after long-term supplementation, the erection (25.89%) and overall satisfaction (33.33%) domains. The present study showed improvement in sexual function upon completing the E. longifolia supplementation programme, providing evidence of E. longifolia acting as an aphrodisiac, a substance that increases sexual desire, sexual attraction, sexual pleasure, or sexual behaviour. The effect of E. longifolia following the 8-week supplementation showed no improvements in isokinetic strength or anaerobic power. Hence, the supplementation of E. longifolia alone did not exhibit any ergogenic effects among young adults, which may be due to the lack of changes in the circulating testosterone levels after 8-weeks of E. longifolia supplementation. In conclusion, the cytotoxicity test demonstrated that E. longifolia has lower lactate dehydrogenase activity in the SMC, suggesting low toxicity levels. While current results show an increase in testosterone level after short-term supplementation, findings also provided evidence that E. longifolia did not influence the hypothalamic-pituitary-gonadal (HPG) axis. Supplementation of E. longifolia improved mood state and sexual function, providing further evidence of the use of E. longifolia as an adaptogen and aphrodisiac. Results also showed 600 mg of E. longifolia alone, the highest dose permitted at present, does not have any ergogenic effects on strength or power.